I had to order a new 7 wire plug harness for my truck. I apparently got the wrong one so we tested the wires and had to cut the plugs off to wire together. Have everything but the trailer brakes working. On my trucks wiring, there are 2 small blue wires that are identical. Blue should be for trailer brakes but which one? we have tried both with no luck.

 

Welcome to the site..

Equipped with OE trailer brake control?

 

It has an aftermarket brake controller. Both of the blue wires are hot whenever the key is on. They both are part of the factory harness. When we disconnected the controller wire in the truck they both were no longer hot. I cannot find any wire diagram for my truck that shows the 2 blue wires yet they are part of the factory harness.